Multibeam electron gun having means for supporting a screen grid electrode relative to a main focusing lens

Abstract

An electron gun for a cathode-ray tube comprises a modular beam-forming region assembly and a main focusing lens which are affixed to at least two insulative support rods. The modular beam-forming region assembly includes a plurality of cathode assemblies, a control grid electrode and a screen grid electrode. The control grid electrode and the screen grid electrode are attached to a first major surface, of a common ceramic member and the cathode assemblies are attached to a second major surface thereof. A transition member is disposed between a metallized pattern on the first major surface of the ceramic member and the screen grid electrode. The transition member includes a substantially flat portion attached to the metallized pattern and two upright portions substantially perpendicular to the flat portion and substantially parallel to each other. The screen grid electrode is disposed between the upright portions and connected thereto by a plurality of step-like support members. Each of the step-like support members includes a screen grid electrode contact portion, a bead support contact portion and a central riser portion extending between the contact portions. The screen grid electrode contact portion of each step-like support member is attached to the screen grid electrode. The bead support contact portion of each step-like support member is attached to a different one of a plurality of bead support members affixed to the insulative support rods, whereby the screen grid electrode is longitudinally spaced from the main focusing lens.

What is claimed is: 
     
       1. In a multibeam electron gun for a cathode-ray tube comprising a modular beam-forming region assembly and a main focusing lens which are affixed to at least two insulative support rods, said beam-forming region assembly including a plurality of cathode assemblies, a control grid electrode and a screen grid electrode, said electrodes having aligned apertures therethrough for passage of a plurality of electron beams from said cathode assemblies, said cathode assemblies and said electrodes being individually held in position from a common ceramic member having a first and a second major surface with a metallized pattern formed on at least a portion of each major surface, said electrodes being attached to said first major surface and said cathode assemblies being attached to said second major surface, wherein the improvement comprises a transition member disposed between said metallized pattern on said first major surface of said ceramic member and said screen grid electrode, said transition member including a substantially flat portion attached to said metallized pattern and two upright portions substantially perpendicular to said flat portion and substantially parallel to each other,   said screen grid electrode having at least one plate-like member disposed between sald upright portions of said transition member, and   a plurality of step-like support members interconnecting said screen grid electrode to said upright portions of said transition member, each of said step-like support members having a screen grid electrode contact portion, a bead support contact portion and a central riser portion extending between said aforementioned contact portions, said screen grid electrode contact portion of each of said step-like support members being attached to said screen grid electrode and said central riser portion of each of said step-like support members being attached to said upright portions of said transition member in longitudinal spaced relation to said control grid electrode, said bead support contact portion of each step-like support member being attached to a different one of a plurality of bead support members affixed to said insulative support rods, whereby said screen grid electrode is longitudinally spaced from said main focusing lens.   
     
     
       2. In a multibeam electron gun for a cathode-ray tube comprising a modular beam-forming region assembly and at least one main focusing lens attached to at least two insulative support rods, said beam-forming region assembly including a plurality of cathode assemblies, a control grid electrode and a screen grid electrode, each of said electrodes having a plurality of aligned apertures therethrough for passage of electron beams from said cathode assemblies, said cathode assemblies and said electrodes being individually held in position from a common ceramic member, said ceramic member having a first major surface and an oppositely disposed second major surface with a metallized pattern formed on at least a portion of each major surface, said control grid electrode and said screen grid electrode being attached to said first major surface and said cathode assemblies being attached to said second major surface, wherein the improvement comprises a transition member attached to said metallized pattern on said first major surface of said ceramic member, said transition member including a substantially flat first part and a second part electrically isolated from said first part, said second part having a flat portion and two upright portions substantially perpendicular to said flat portion and substantially parallel to each other,   said control grid electrode being attached to said first part of said transition member,   said screen grid electrode comprising at least one plate-like member, and   a plurality of step-like support members interconnecting said screen grid electrode and said upright portions of said second part of said transition member, each of said step-like support members including a screen grid electrode contact portion, a bead support contact portion and a central riser portion of precise length extending between said contact portions, each of said screen grid electrode contact portions being attached to said screen grid electrode, said screen grid electrode being disposed between said upright portions of said transition member, said central riser portion of each of said support members being adjacent to said upright portions of said transition member and attached thereto, whereby said screen grid electrode can be positioned laterally and longitudinally with respect to said control grid electrode and secured in alignment therewith, each of said bead support contact portions being attached to a different one of a plurality of bead support members affixed to said insulative support rods, thereby locating said screen grid electrode of said modular beam-forming region assembly in longitudinally spaced relation to said main focusing lens.   
     
     
       3. In an inline electron gun for a cathode-ray tube comprising a modular beam-forming region assembly and at least one main focusing lens attached to at least two insulative support rods, said beam-forming region assembly including three cathode assemblies, a control grid electrode and a screen grid electrode, each of said electrodes having three aligned apertures therethrough for passage of electron beams from said cathode assemblies, said cathode assemblies and said electrodes being individually held in position from a common ceramic member, said ceramic member having a first major surface and an oppositely disposed second major surface with a metallized pattern formed on at least a portion of each major surface, said control grid electrode and said screen grid electrode being attached to said first major surface and said cathode assemblies being attached to said second major surface, wherein the improvement comprises a bimetal transition member attached to said metallized pattern on said first major surface of said ceramic member, said transition member including a substantially flat first part and a second part electrically isolated from said first part, said second part having a flat portion and two upright portions substantially perpendicular to said flat portion and substantially parallel to each other,   said control grid electrode being attached to said first part of said transition member,   said screen grid electrode comprising three separate plate-like portions, each portion having one of said apertures therein, and   a plurality of step-like support members interconnecting each of said plate-like portions of said screen grid electrode and said upright portions of said second part of said transition member, each of said step-like support members including a screen grid electrode contact portion, a bead support contact portion and a central riser portion of precise length extending between said contact portions, said screen grid electrode contact portions being attached to said plate-like portions of said screen grid electrode, said plate-like portions of said screen grid electrode being disposed between said upright portions of said transition member, said central riser portion of each of said support members being adjacent to said upright portions of said transition member and attached thereto, whereby said plate-like portions of said screen grid electrode can be positioned laterally and longitudinally with respect to said control grid electrode and secured in alignment therewith, each of said bead support contact portions being attached to a different one of a plurality of bead support members affixed to said insulative support rods, thereby attaching said screen grid electrode of said modular beam-forming region assembly in longitudinal spaced relation to said main focusing lens.